Most plants cannot put every machine on a preventive maintenance (PM) schedule in one go. There are too many assets, too few technicians and not enough time. So the first decision is which equipment goes first. A criticality ranking answers that with a score instead of an argument. This guide gives you a four-factor method you can finish in an afternoon. Once you have your ranking, use the PM schedule generator to build the plan for your top-ranked equipment.

Why Ranking Comes Before Scheduling

If you start with the machine that gets the loudest complaints, you schedule by noise. If you start with the oldest machine, you schedule by habit. Neither tells you which failure would hurt most.

A ranking fixes that. It makes you ask the same four questions about every asset, so the decision is consistent and easy to explain to a plant head or a production manager.

The Four Questions to Score

Give each asset a score from 1 (low) to 3 (high) on each question:

1. Safety and compliance. Could a failure injure someone, cause a spill or break a rule? Score 3 if yes, and 1 if the risk is negligible. Equipment with statutory or regulatory inspections should be treated as top priority whatever its score.

2. Production impact. If it stops, what happens to output? Score 3 if the line stops, 2 if output drops, and 1 if production carries on.

3. Backup available. Score 3 if there is no standby, 2 if a standby exists but needs work to bring online, and 1 if a ready standby or spare takes over.

4. Repair cost and lead time. Score 3 if repairs are expensive or parts take weeks to arrive, 2 if moderate, and 1 if cheap and available from stores.

Add the four scores. The total runs from 4 to 12.

Worked Example: Six Assets

Here is a sample plant. The scores are illustrative, so use your own.

Turn Scores Into Priority Tiers

Group the totals into three tiers:

In the example, the boiler and the main process pump are tier A. The compressor and chiller are tier B. The conveyor motor and exhaust fan are tier C.

Tier C does not mean ignored. A cheap motor with a spare on the shelf can be a sensible run-to-failure candidate. That should be a deliberate decision, not neglect.

Check the Ranking Before You Trust It

Before you finalise, run three quick checks:

• Does anything surprise you? If a minor machine scores high, one of your scores is probably wrong. Fix the score, not the ranking.

• Ask the people who run it. Operators and technicians often know failure patterns that are not in any record.

• Look at failure history. An asset that keeps breaking down deserves attention even if its score is average.

Feed Your Top Tier Into the Generator

Now you can build the schedule in order of importance:

1. Pick your tier A equipment in the generator, and set the number of units you have.

2. Check the workload chart. If tier A alone already fills your technicians' time, you know to add resources before adding more assets.

3. Add tier B and look at the chart again. Stop adding when the workload is more than your team can deliver.

4. Leave tier C for later, once tier A and B are running reliably.

The generator covers five equipment types: pumps, screw compressors, LT induction motors, small and medium package boilers and water-cooled chillers. For other equipment, use the same ranking and build the task list from the manufacturer's manual.

Review the Ranking Every Year

Criticality changes. A new production line, a removed backup or a repeated failure can all move an asset up a tier. Review the scores once a year, and any time you change the process.

When your asset list grows, keeping scores, schedules and completion records in a spreadsheet gets harder. A CMMS keeps criticality, tasks and compliance together, as described in our preventive maintenance software module.

Frequently Asked Questions

How many assets should I schedule first?

Start with only as many as your team can complete reliably. A smaller schedule that is fully followed is worth more than a large one that slips.

Should I score by machine or by component?

Start with the machine. Break an asset into components only when one part, such as a critical gearbox, needs its own schedule.

What if two assets have the same score?

Break the tie using failure history. The asset that has failed more often goes first.

Rank First, Then Schedule

A short ranking exercise saves months of effort on the wrong machines. Score your assets, sort them into tiers and build your first schedule around tier A.

If you want criticality, schedules and PM compliance managed in one place, book a free 30-minute demo with PlantOps360 and we will show you how it works with a plant like yours.